Jeffrey Barker said:

I recently read in a gardening book that high-density sodium lamps
were much better than any other type of lamp to use as grow-lights.

They produce more lumens of light per watt. But as to best, that depends
on what you plan to do with them.

It seems that high-density sodium lamps are the same type used for
streetlights and home security.

The ones with the weird orange color.

Does anyone know if this is the case? If so, I'd rather drop $20 or
so on a huge lamp that would (I imagine) be useful for all of my
seedlings and plants, since it's so bright, instead of several
flourescent lamps, which need to be kept very close to the plants.

Metal halide lamps will produce better tseedlings for transplant than
high pressure sodium. Their spectrum is much closer to that of sunlight.
The light output of a sodium lamp is all in the long (orange/red) wavelengths
and will lead to a leggier plants. Sodium lamps are often used as
supplemental light in greenhouses, because the long wavelength light
encourages blooms. The greenhouse plants get enough natural sunlight
with short (blue) wavelegths to keep them from getting leggy.

In my opinion if you want to put large amounts of light into a compact space,
metal halide lamps are the way to go. I use a 250 watt metal halide lamp for
starting all of my tomatoes, peppers, and eggplants. But I also have a couple of
flourescent fixtures which I use as supplementary light for starting bedding
flowers in an east-facing window.
--
Pat in Plymouth MI

Any technology distinguishable from magic is insufficiently advanced.
(attributed to Don Marti)